Method of treating tissue with radio frequency vascular electrode array

ABSTRACT

A method of treating a patient is provided. The method comprises delivering an electrically conductive material within a vascular network, wherein the electrically conductive material embolizes in a region of the vascular network to form a vascular electrode array that assumes a geometry of the embolized region of the vascular network. The method may optionally comprise delivering a containment agent within the vascular network proximal to the delivered electrically conductive material to stabilize the vascular electrode array. The method further comprises applying electrical energy (e.g., radio frequency (RF) energy) to the vascular electrode array to therapeutically conduct electrical energy into a region of the targeted tissue adjacent the embolized region of the vascular network.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims benefit of provisional application U.S.Ser. No. 60/755,738, filed Dec. 29, 2005, the entire disclosure of whichis hereby incorporated by reference herein.

FIELD OF THE INVENTION

The field of the invention relates generally to the treatment of solidtissue, e.g., tumors, using radio frequency (RF) ablation energy.

BACKGROUND OF THE INVENTION

The delivery of radio frequency (RF) energy to target regions withinsolid tissue is known for a variety of purposes of particular interestto the present inventions. In one particular application, RF energy maybe delivered to diseased regions (e.g., tumors) in targeted tissue forthe purpose of tissue necrosis. RF ablation of tumors is currentlyperformed within one of two core technologies.

The first technology uses a single needle electrode, which when attachedto a RF generator, emits RF energy from the exposed, uninsulated portionof the electrode. This energy translates into ion agitation, which isconverted into heat and induces cellular death via coagulation necrosis.The second technology utilizes multiple needle electrodes, which havebeen designed for the treatment and necrosis of tumors in the liver andother solid tissues. PCT application WO 96/29946 and U.S. Pat. No.6,379,353 disclose such probes. In U.S. Pat. No. 6,379,353, a probesystem comprises a cannula having a needle electrode arrayreciprocatably mounted therein. The individual electrodes within thearray have spring memory, so that they assume a radially outward,arcuate configuration as they are advanced distally from the cannula.

In theory, RF ablation can be used to sculpt precisely the volume ofnecrosis to match the extent of the tumor. By varying the power outputand the type of electrical waveform, it is possible to control theextent of heating, and thus, the resulting ablation. However, the sizeof tissue coagulation created from a single electrode, and to a lesserextent a multiple electrode array, has been limited by heat dispersion.As a consequence, when ablating lesions that are larger than thecapability of the above-mentioned devices, the common practice is tostack ablations (i.e., perform multiple ablations) within a given area.This requires multiple electrode placements and ablations facilitated bythe use of ultrasound imaging to visualize the electrode in relation tothe targeted tissue. Because of the echogenic cloud created by theablated tissue, however, this process often becomes difficult toaccurately perform. This process considerably increases treatmentduration and patent discomfort and requires significant skill formeticulous precision of probe placement.

In response to this, the marketplace has attempted to create largerlesions with a single probe insertion. Increasing generator output,however, has been generally unsuccessful for increasing lesion diameter,because an increased wattage is associated with a local increase oftemperature to more than 100° C., which induces tissue vaporization andcharring. This then increases local tissue impedance, limiting RFdeposition, and therefore heat diffusion and associated coagulationnecrosis. In addition, patient tolerance appears to be at the maximumusing currently available 200 W generators.

It has been shown that the introduction of conductive fluid, such assaline, into the extra-cellular spaces of the targeted tissue increasesthe tissue conductivity, thereby creating a larger lesion size. However,because electrically conductive fluid may preferentially travel intofissures or spaces inside, and even outside, of the targeted tissue,application of ablation energy to the targeted tissue may result inirregular ablation shapes that may include healthy tissue.

For this reason, it would be desirable to provide improvedelectrosurgical methods and systems for more efficiently and effectivelyablating tumors in the liver and other body organs that are larger thanthe single ablation capability of the electrode or electrode array onthe electrosurgical device being used.

SUMMARY OF THE INVENTION

In accordance with the present inventions, a method of treating apatient is provided. The method comprises delivering an electricallyconductive material within a vascular network, wherein the electricallyconductive material embolizes in a region of the vascular network. Thevascular network may be, e.g., a network of blood vessels, although thevascular network can be any physiological network in a patent throughwhich fluid (liquid or air) flows. The embolic material may have aviscosity that, when introduced into the vascular network, allows theembolic material to naturally flow through the vascular network. Thevascular network may comprise vessels that reduce in size at a peripheryof the targeted tissue, and the electrically conductive material maycomprise particles, each of which is sized to lodge within a vessel atthe periphery of the targeted tissue. In one method, the electricallyconductive material comprises embolic particles suspended within anelectrically conductive solution. In another method, the electricallyconductive material comprises embolic particles doped with metallicsub-particles.

The embolic material forms a vascular electrode array that assumes ageometry of the embolized region of the vascular network. The vascularelectrode array may comprise a main shaft (e.g., corresponding to a maintrunk of the vascular network) and an array of tines extending from themain shaft (e.g., corresponding to vessels extending from the maintrunk). The method may optionally comprise delivering a containmentagent within the vascular network proximal to the delivered electricallyconductive material to stabilize the vascular electrode array.

The method further comprises applying electrical energy (e.g., radiofrequency (RF) energy) to the vascular electrode array totherapeutically conduct electrical energy into a region of the targetedtissue adjacent the embolized region of the vascular network. In onemethod, the electrical energy therapeutically ablates the targetedtissue. The embolic material may have a viscosity that, when theelectrical energy is applied, prevents the vascular network fromclosing. In this manner, electrical disconnects within the vascularelectrode array are prevented or minimized. The embolized region of thevascular network may comprise the entirety of the vascular network, andthe adjacent region of the targeted tissue may comprise the entirety ofthe targeted tissue, although less than the entirety of the vascularnetwork may be embolized, and less than the targeted tissue can beexposed to the electrical energy. In one method, the electricallyconductive material is introduced into the vascular network and theelectrical energy is applied to the vascular electrode array via asingle probe, although separate probes may be used to perform therespective functions.

In an optional method, the embolic material may be biologicallynon-resorbable, so that the vascular electrode array is permanent orsemi-permanent. In this case, the method may further comprise applyingadditional electrical energy to the vascular electrode array, wherebythe additional electrical energy is therapeutically conducted into anyanomalies in the corresponding region of targeted tissue region thathave occurred after the previous application of electrical energy.

In one method, targeted tissue external to the vascular network istreated. The vascular network is contoured to the general shape and sizeof the targeted tissue is provided, in which case, the vascularelectrode array formed by the embolic material is likewise contoured tothe general shape and size of the targeted tissue. Thus, it can beappreciated the electrical energy applied to the vascular electrodearray is efficiently and effectively conveyed into the targeted tissue.This method lends itself well to the treatment of tumors, which aretypically highly vascularized. In another method, an abnormality withinthe vascular network is treated. The abnormality may be, e.g., ahemorrhage or some other vascular abnormality, such as an ArterioVascular Malformation (AVM), Arterio Vascular Fistula (AVF), VenousMalformation (VM), or Lymphatic Malformation (LM).

In another method, an electrically conductive material, which need notbe embolic in nature, is delivered. The electrically conductive materialhas a viscosity that, when introduced into the vascular network, allowsthe electrically conductive material to naturally flow through thevascular network. In this case, the method further comprises deliveringa containment agent within the vascular network proximal to thedelivered electrically conductive material to stabilize the electricallyconductive material, thereby forming a vascular electrode array thatassumes a geometry of the vascular network. Electrical energy is thenapplied to the vascular electrode array to therapeutically conductelectrical energy into the vascular network.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 is a perspective view of tissue treatment system constructed inaccordance with a preferred embodiment of the present inventions;

FIG. 2 is a perspective view of a tissue treatment kit arranged inaccordance with a preferred embodiment of the present inventions;

FIGS. 3A-3F illustrate views of one preferred method of using the tissuetreatment system of FIG. 1 to treat a vascularized tumor;

FIGS. 4A-4D illustrate views of one preferred method of using the tissuetreatment kit of FIG. 2 to treat a vascularized tumor.

DETAILED DESCRIPTION OF THE ILLUSTRATED SYSTEMS AND METHODS

Referring to FIG. 1, one embodiment of a tissue treatment system 10constructed in accordance with the present inventions will now bedescribed. The tissue treatment system 10 generally comprises anintravascular treatment catheter 12, a source of an electricallyconductive embolic material 14, a source of inflation medium 16, and asource of ablation energy, and in particular, a radio frequency (RF)generator 18. As will be described in further detail below, the tissuetreatment system 10 may be operated to deliver an electricallyconductive material within a vascular network. The vascular network maybe, e.g., a network of blood vessels. The electrically conductivematerial is designed to embolize the vascular network or at least aregion thereof, which can then be stabilized to form a vascularelectrode array. This vascular electrode array can then be energizedwith electrical energy, e.g., radio frequency (RF) energy, to treattissue adjacent the vascular network, e.g., a tumor, or even to treatthe vascular network itself.

The catheter 12 comprises an elongated flexible shaft 20 that can beconveniently delivered to a target region via the vasculature of apatient. The catheter 12 further comprises an embolic material deliveryport 22 located at the distal tip of the catheter shaft 20, aninflatable balloon 24 mounted to the distal end of the catheter shaft20, and a radio frequency (RF) electrode 26 suitably mounted to thedistal end of the catheter shaft 20 between the embolic materialdelivery port 22 and balloon 24. The catheter 12 also comprises a handle28 suitably mounted to the proximal end of the catheter shaft 20, and anembolic material entry port 30, balloon inflation port 32, andelectrical connector 34 located on the handle 28. The embolic materialentry port 30 and balloon inflation port 32 are fluidly coupled to therespective embolic delivery port 22 and balloon 24 via lumens (notshown) extending through the catheter shaft 20. The electrical connector34 is electrically coupled to the electrode 26 via a radio frequency(RF) wire (not shown) extending through the catheter shaft 20.

The embolic material source 14 is mated to the embolic entry port 30 onthe handle 28 via a tube 36, so that embolic material can be deliveredfrom the source 14 out through the delivery port 22 into a vessel of thevascular network in which the distal end of the catheter shaft 20resides. In the illustrated embodiment, the embolic material source 14comprises a standard syringe filled with the embolic material.Alternatively, a pump or other suitable mechanism for conveying embolicmaterial under positive pressure can be used.

The embolic material has an initial viscosity that allows the embolicmaterial to easily flow through the vascular network in which theembolic material is intended to be delivered. At the time that theembolic material is stabilized into a vascular electrode array, theviscosity of the embolic material may increase depending on thetreatment. For example, in certain treatments, it is preferable todesign the embolic material, such that it hardens over a period of time,whereas there may be other treatments in which it is preferable todesign the embolic material, such that it maintains a relatively lowviscosity over time.

In the illustrated embodiment, the embolic material containsnon-electrically conductive solid particles, such as microspheres orpolyvinyl acetate (PVA) strings, that are capable of lodging withinsmall vessels of the vascular network. As briefly stated above, theembolic material, as a whole, is electrically conductive, which for thepurposes of this specification, means that the embolic material has aresistivity substantially lower than that of tissue, such as blood, sothat electrical energy applied to the delivered embolic materialpreferentially uses the embolic material as a conductive path comparedto the tissue that surrounds the embolic material. To this end, theembolic material comprises a highly electrically conductive solution,such as, e.g., calcium chloride, sodium chloride, etc., in which theembolic particles are suspended.

In optional embodiments, the electrically non-conductive embolicparticles may be doped with metallic sub-particles, such as iron,silver, gold, etc., to render the embolic particles themselveselectrically conductive. Or, instead of using embolic particles,electrically conductive devices, such as embolic coils, can be used. Ineither case, a solution, whether electrically conductive or not, is usedto suspend, and therefore allow, the embolic particles or devices toeasily flow through the vascular network in the presence of relativelysmall pressures.

In other optional embodiments, the embolic material, (i.e., thecombination of the embolic particles and solution) is configured toharden in response to certain conditions, e.g., passage of time,temperature, and/or pH of environment. In these cases, it is possiblethat a containment mechanism, such as the balloon 24 is not needed,depending on the time that it takes for the embolic material to harden.As an example, the embolic material may take the form of a polymerizingor phase transition liquid that contains electrically conductiveparticles (e.g., ferritic, silver, gold, etc.) and that hardens or setsin response to these conditions. Or an electrically conductive fibrinsealant, such as Tisseel®, may be used as the embolic material. In otheroptional embodiments, the embolic material may be non-resorbable, sothat the resulting vascular electrode array is permanent orsemi-permanent. Suitable non-resorbable embolic materials includepolyvinyl alcohol and cyanoacrylates. As will be described in furtherdetail below, this allows subsequent treatments to be rendered. Any ofthe above-mentioned embolic materials may be enhanced with contrastagents and/or echogenic particles that would allow visualization of theembolic material using common imaging technologies, such as afluoroscope or ultrasound imager.

In the illustrated embodiment, the single source 14 contains the embolicmaterial. However, if the electrically conductive embolic material isdesigned to be formed by the mixing of separate components within thevascular network (e.g., embolic particles suspended within anelectrically conductive solution, or the separate components of a tissuesealant), the components can be separately delivered from the distal endof the catheter shaft 20 where it naturally combines within the bloodvessel to form the electrically conductive embolic material. In thiscase, two separate sources can be used to separately contain thecomponents, in which case, an additional entry port, lumen, and deliveryport (all not shown) will need to be incorporated into the catheter 12.Alternatively, the same source can be used to contain the components atdifferent times. For example, the source 14 can be used to deliver onecomponent via the delivery port 22, and then a second component via thesame delivery port 22.

The inflation medium source 16 is mated to the balloon inflation port 32on the handle 28 via a tube 38, so that inflation medium (e.g., saline)can be delivered from the source 16 into the interior of the balloon 24,thereby expanding the balloon 24 within the vessel of the vascularnetwork in which the distal end of the catheter shaft 20 resides. In theillustrated embodiment, the inflation medium source 16 comprises astandard syringe filled within the inflation medium. Alternatively, apump or other suitable mechanism for conveying the inflation mediumunder positive pressure can be used. As will be described in furtherdetail below, inflation of the balloon 24 within the vessel effectivelycontains the embolic material within the region of the vascular networkthat is distal to the inflated balloon 24. In this manner, theelectrically conductive embolic material becomes stabilized, therebytransforming it into a vascular electrode array. Inflation of theballoon 24 may also prevent or minimize the dilution of the electricallyconductive embolic material, which may otherwise occur if blood wasallowed to flow into the region of the vascular network occupied by theembolic material.

In alternative embodiments, instead of, or in addition to, using aballoon, other mechanisms can be used to contain the embolic material.For example, a powdered gelfoam mixed in a solution, such as salineand/or contrast agent, large PVA spheres, coils that induce thrombusformation, or a polymerizing or phase transition material thathardens/sets in response to certain conditions, can be delivered intothe vascular network proximal to the embolic material. In this case, aseparate source of the containment agent, delivery port, lumen, andentry port can be provided on the catheter 12. Alternatively, themechanism used to deliver the electrically conductive embolic materialcan be used to subsequently deliver the containment agent.

The RF generator 18 is mated to the electrical connector 34 on thehandle 28 via a RF cable 40, so that RF energy can be delivered from theRF generator 18 to the electrode 26. The RF generator 18 may be aconventional RF power supply that operates at a frequency in the rangefrom 200 kHz to 9.5 MHz, with a conventional sinusoidal ornon-sinusoidal wave form. In the illustrated embodiment, the RF currentis delivered to the electrode 26 in a monopolar fashion, which meansthat current will pass from the electrode 26, which is configured toconcentrate the energy flux in order to have an injurious effect on thesurrounding tissue, and a dispersive electrode (not shown), which islocated remotely from the electrode 26 and has a sufficiently large area(typically 130 cm² for an adult), so that the current density is low andnon-injurious to surrounding tissue. In the illustrated embodiment, thedispersive electrode may be attached externally to the patient, e.g.,using a contact pad placed on the patient's flank. Alternatively, the RFcurrent is delivered to the electrode 26 in a bipolar fashion, whichmeans that current will pass from the electrode 26 to another electrodewithin the patient's body.

While the mechanisms for delivering and containing the electricallyconductive embolic material within a vascular network, and applying RFablation energy to the resulting vascular electrode array areimplemented in a single intravascular catheter, as illustrated in FIG.1, it should be appreciated that the mechanisms can be implemented inseparate catheters. For example, one catheter can be used to deliver andcontain the embolic material, and another catheter can be used to applyRF ablation energy to the resulting vascular electrode array. Also, suchmechanisms can be implemented in one or more rigid probes that can bepercutaneously introduced through the patient's skin directly into thetreatment region for delivery and containment of the embolic materialand application of RF energy.

For example, referring to FIG. 2, a tissue treatment kit 50 constructedin accordance with the present inventions will now be described. Thetissue treatment kit 50 is configured for percutaneously treating apatient, and generally comprises a separate embolic material deliveryprobe 52, vessel occlusion probe 54, and tissue ablation probe 56.

The embolic material delivery probe 52 comprises an elongated shaft 58composed of a rigid or semi-rigid material, such that the probe 52 canbe introduced through solid tissue to the targeted tissue. The probe 52may optionally be introduced to the targeted tissue via a cannula (notshown). To facilitate introduction through solid tissue, the distal endof the probe shaft 58 has an open tissue-penetrating tip 60. The embolicmaterial delivery probe 52 also comprises an embolic material deliveryport 62 located at the distal tip of the probe shaft 58 and a deliverylumen (not shown) extending through the probe shaft 58 in fluidcommunication with the delivery port 62. The embolic material deliveryprobe 52 further comprises a handle 64 mounted to the proximal end ofthe probe shaft 58, and an embolic material entry port 66 disposed onthe handle 64 for mating with the embolic material source 14 (shown inFIG. 1). In the same manner described above, embolic material can beconveyed from the source 14 out through the delivery port 62 at thedistal end of the probe shaft 58. The embolic material may be any one ormore of the varying compositions described above.

The vessel occlusion probe 54 comprises an elongated shaft 68 composedof a rigid or semi-rigid material, such that the probe 54 can beintroduced through solid tissue to the targeted tissue. The probe 54 mayoptionally be introduced to the targeted tissue via a cannula (notshown). To facilitate introduction through solid tissue, the distal endof the probe shaft 68 has an open tissue-penetrating tip 70. The vesselocclusion probe 54 also comprises a balloon 72 located at the distal tipof the probe shaft 68 and a delivery lumen (not shown) extending throughthe probe shaft 68 in fluid communication with the interior of theballoon 72. The vessel occlusion probe 54 further comprises a handle 74mounted to the proximal end of the probe shaft 68, and an inflationmedium entry port 76 disposed on the handle 74 for mating with theinflation medium source 16 (shown in FIG. 1). In the same mannerdescribed above, inflation medium can be conveyed from the source 16 toinflate the balloon 72 at the distal end of the probe shaft 68.Alternatively, rather than using the balloon 72 or in addition to theballoon 72, vessel occlusive materials, such as any one or more of thecontainment agents described above, can be delivered through a lumen(not shown) within the vessel occlusion probe 54.

In the illustrated embodiment, the tissue ablation probe 56 takes theform of a single-needle ablation probe. The ablation probe 56 comprisesan elongated shaft 78 composed of a rigid or semi-rigid material, suchthat the probe 56 can be introduced through solid tissue to the targetedtissue. The probe 56 may optionally be introduced to the targeted tissuevia a cannula (not shown). To facilitate introduction through solidtissue, the distal end of the probe shaft 78 has a closedtissue-penetrating tip 80. The ablation probe 56 further comprises anelectrode 82 carried by the distal end of the probe shaft 78. In theillustrated embodiment, the probe shaft 78 is composed of anelectrically conductive material, such as stainless steel, and anelectrically insulative coating can be applied to the probe shaft 78, inwhich case, an uninsulated portion of the probe shaft 78 can form theelectrode 82. Alternatively, the probe shaft 78 may be composed of anelectrically insulative material, and the distal end of the probe shaft78 can be coated with an electrically conductive material to form theelectrode 82. The ablation probe 78 further comprises a handle 84mounted to the proximal end of the probe shaft 78, and an electricalconnector 86 disposed within the handle 84 for electrically coupling tothe RF generator 18 (shown in FIG. 1). In the same manner describedabove, RF energy can be conveyed from the RF generator 18 to theelectrode 82 in a monopolar arrangement, although such RF energy can bealternatively conveyed in a bipolar arrangement. In alternativeembodiments, ablation probes with deployable needle electrodes may beused, although, to a certain extent, the use of a vascular electrodearray to ablate the targeted tissue obviates the need to use amulti-electrode ablation probe.

One method of treating targeted tissue, and in particular, a tumor, willnow be described. The targeted tissue may be located anywhere in thebody where hyperthermic exposure may be beneficial. Most commonly, thetargeted tissue will comprise a solid tumor within an organ of the body,such as the liver, kidney, pancreas, breast, prostrate (not accessed viathe urethra), and the like. The volume to be treated will depend on thesize of the tumor or other lesion, typically having a total volume from1 cm³ to 150 cm³, and often from 2 cm³ to 50 cm³ The peripheraldimensions of the treatment region will usually be regular, e.g.,spherical or ellipsoidal, but will more usually be irregular. Thetreatment region may be identified using conventional imaging techniquescapable of elucidating a targeted tissue, e.g., tumor tissue, such asultrasonic scanning, magnetic resonance imaging (MRI), computer-assistedtomography (CAT), fluoroscopy, nuclear scanning (using radiolabeledtumor-specific probes), and the like. Preferred is the use of highresolution ultrasound of the tumor or other lesion being treated, eitherintraoperatively or externally.

Referring to FIGS. 3A-3F, a method of treating a tumor with the tissuetreatment system 10 illustrated in FIG. 1 will now be described. In themethod specifically illustrated, the targeted tissue takes the form of atumor T with an associated network of blood vessels VN that suppliesblood to nourish the tumor T (FIG. 3A). As shown, the network VNcomprises a main trunk TR with smaller vessel branches BR (e.g.,arteries), which lead to even smaller peripheral vessels P (e.g.,arterioles and capillaries). Significantly, because tumors are highlyvascularized, the vessel network VN is physically contoured to thegeneral shape and size of the tumor T. The treatment method takesadvantage of this to create a vascular electrode array that is alsophysiologically contoured to the shape and size of the tumor T. As willbe discussed in further detail, the vascular electrode array can beenergized, i.e., ablation energy can be applied to the electrode array,which is then distributed to the surrounding tumor, resulting in theeffective and efficient ablation of the tumor T.

To create the vascular electrode array, the catheter 12 is firstconventionally introduced though the vasculature of the patient from anentry point (e.g., a puncture within the femoral artery) until thedistal end of the catheter 12 resides within the vessel network VN orproximal thereto (FIG. 3B). In the illustrated embodiment, the distalend of the catheter 12 is located within the main trunk TR of the vesselnetwork VN, which supplies the remaining vessels of the network VN withblood.

Next, the electrically conductive embolic material EM is delivered fromthe embolic material source 14 (shown in FIG. 1) through the catheter 12and out of the delivery port 22 into the trunk TR of the vessel networkVN, where it is conveyed into the vessel branches BR and smallerperipheral vessels P (FIG. 3C). The blood flow facilitates the perfusionof the embolic material EM throughout the vessel network VN. The solidparticles suspended within the solution of the embolic material EM willflow into and lodge within the smaller peripheral vessels P, therebyallowing proximal branch BR vessels and trunk T to fill with the embolicmaterial EM (FIG. 3D). In an alternative method, the electricallyconductive solution in which the solid particles are suspended may bedelivered prior or subsequent to the delivery of the solid embolicparticles, which then combine within the vessel network VN to form theelectrically conductive embolic material EM. From this, it can beappreciated that the selection of an arterial network for distributionof the embolic material EM is superior, since the embolic material canbe introduced into a single artery where it is distributed to the manybranches (arterioles, capillaries) that supply the tumor T with blood.If the embolic material EM comprises a radiopaque or echogenic material,the tumor T may be fluoroscopically or ultrasonically imaged to confirmthat the vessel network VN is filled with the embolic material EM.

Next, the inflation medium is delivered from the source 16 (shown inFIG. 1) through the catheter 12 and into the interior of the balloon 24to inflate it, thereby containing and stabilizing the embolic materialEM within the vessel network VN (FIG. 3E). In alternative methods,rather than expanding a balloon 24, other containments mechanisms, suchas those previously discussed above, can be delivered from the catheter12 into the vascular network VN. In the case where the embolic materialis self-stabilizing, e.g., if the embolic material is configured toquickly harden in response to environmental conditions, expansion of aballoon 24 or the use of any containment mechanism may not be necessary.

In any event, the stabilized embolic material EM assumes the geometry ofthe vessel network VN to form a vascular electrode array. As can beseen, the portion of the vascular electrode array corresponding to thetrunk T of the vessel network VN can be considered the shaft of theelectrode array, and the portions of the vascular electrode arraycorresponding to the vessel branches BR and peripheral vessels P of thevessel network VN can be considered the tines of the electrode array. Inthe preferred method, the embolic material EM hardens, e.g., naturallyover a period of time or in response to the pH of the blood or increasedtemperature within the vessel network VN. In this manner, the embolicmaterial EM resists closure of the lumens of the vessel network VN,which may otherwise occur during subsequent ablation of the tumor T.

While the electrode 26 is in contact with the vascular electrode array,RF energy is conveyed from the RF generator 18 (shown in FIG. 1) throughthe catheter 12 to the electrode 26 (FIG. 3F). The RF energy (shown asarrows) is in turn conveyed from the electrode 26 through the vascularelectrode array and into the surrounding tumor T, thereby ablating thetumor T. Alternatively, the electrode 26 may not be in contact with thevascular electrode array when the RF energy is conveyed from the RFgenerator 18. In this case, because of the electrical conductivity ofthe tissue, and through inductance, the vascular electrode array isindirectly exposed to the RF energy conveyed from the electrode 26 ofthe catheter 12. In either case, RF energy will be distributedthroughout the tumor T to ablate a greater region than what would beablated with just the electrode 26. Notably, because the vascularelectrode array is hard, the vessel network VN will not close, so thatno break is created in the conductive pathway within the vascularelectrode array, so RF energy continues to flow through the tines of thevascular electrode array though the treatment.

In the illustrated method, the entirety of the tumor T is ablated, sincethe vascular electrode array extends through the entirety of the tumorT. Alternatively, a region of the tumor T may be ablated at one time byforming the vascular electrode array within only a region of the vesselnetwork VN, which when activated, ablates the corresponding region ofthe tumor T.

After the initial treatment, the inflation medium is removed from theballoon 24, e.g., by applying a vacuum to the inflation port 32, whichcauses the balloon 24 to deflate, and the catheter 12 is then removedfrom the patient. If the vascular electrode array is non-resorbable,subsequent follow-up treatments can be perform by reapplying RF energyto the vascular electrode array to ablate any remaining portion of thetumor T or ablate any portion of the tumor T that has grown since theinitial treatment.

Referring to FIGS. 4A-4D, a method of treating a tumor with the tissuetreatment kit 50 illustrated in FIG. 2 will now be described. The maindifferences between this method and the method illustrated with respectto FIGS. 3A-3F is the tumor in this method will be treated using threeseparate probes that are directly introduced into the patient's body,whereas a single probe was intravascularly introduced into the patient'sbody in the previous method.

First, the embolic material delivery probe 52 is directly introducedthrough the patient's skin or through an open surgical incision untilthe distal end of the probe 52 resides within the trunk TR of the vesselnetwork VN, and the electrically conductive embolic material EM isdelivered from the embolic material source 14 (shown in FIG. 1) throughthe probe 52 and out of the delivery port 62 into the trunk TR of thevessel network VN, where it is conveyed into the vessel branches BR andsmaller peripheral vessels P (FIG. 4A). In the same manner describedabove, the solid particles suspended within the solution of the embolicmaterial EM will flow into and lodge within the smaller peripheralvessels P, thereby allowing proximal branch BR vessels and trunk T tofill with the embolic material EM (FIG. 4B).

Next, the embolic material delivery probe 52 is removed from thepatient. The vessel occlusion probe 54 is then directly introducedthrough the patient's skin or through an open surgical incision untilthe distal end of the probe 54 resides within the trunk TR of the vesselnetwork VN, and inflation medium is delivered from the source 16 (shownin FIG. 1) through the probe 54 and into the interior of the balloon 72to inflate it, thereby containing and stabilizing the embolic materialEM within the vessel network VN (FIG. 4C). Alternatively, other vesselocclusive agents can be introduced into the trunk TR of the vesselnetwork VN. Once the embolic material EM has been fully stabilized, theballoon 72 is deflated by removing inflation medium out of the inflationmedium entry port 76, and the probe 54 is removed from the patient.

The tissue ablation probe 56 is then directly introduced through thepatient's skin or through an open surgical incision until the electrode82 on the probe 56 is in contact with the vascular electrode array, andRF energy is conveyed from the RF generator 18 (shown in FIG. 1) throughthe probe 56 to the electrode 82 (FIG. 4D). The RF energy (shown asarrows) is in turn conveyed from the electrode 26 through the vascularelectrode array and into the surrounding tumor T, thereby ablating thetumor T. Alternatively, as previously described above, the electrode 82may not be in contact with the vascular electrode array when the RFenergy is conveyed from the RF generator 18, but instead indirectlyexposes the vascular electrode array with RF energy via tissueconductivity and inductance. Once treatment is complete (whether or notsubsequent treatment is needed), the tissue ablation probe 56 is removedfrom the patient.

In the method illustrated in FIGS. 4A-4D, the probes 52, 54, and 56 maybe introduced through the same opening in which the embolic materialdelivery probe 52 was introduced. In an optional method, a separatecannula (not shown) can be used to conveniently deliver the probes 52,54, and 56. That is, the cannula can be initially used to access thetrunk TR of the vessel network VN. While the cannula is left in place,the embolic material delivery probe 52 can then be introduced throughcannula into the trunk TR, exchanged with the vessel occlusion probe 54,which can then be exchanged with the tissue ablation probe 56.Alternatively, while the illustrated method contemplates sequentialdelivery and operation of the probes 52, 54, and 56, two or more of theprobes 52, 54, and 56 can be located in the trunk TR at the same time.For example, if containment of the embolic material must be maintainedby the inflated balloon 72 of the vessel occlusion probe 54 duringtissue ablation, the vessel occlusion probe 54 and tissue ablation probe56 may be located in the trunk TR at the same time, with the electrode82 of the tissue ablation probe 56 being distal to the inflated balloon72. In this case, the probes 52, 54, and 56 may be introduced into thepatient through different openings.

Although the methods illustrated above lend themselves well to thetreatment of tissue outside of blood vessels, vascular electrode arraysmay be formed within other types of vascular networks, such as thebronchial system. For example, the vascular electrode arrays may beformed in a selected portion of the bronchial system and energized totreat cancerous tissue or otherwise necrose specific portions of thelung. This procedure may be equivalent to a Lung Volume Reduction, sincetreated portion of the lung would not be able, after treatment, toexchange gases during respiration.

Although the methods illustrated above lend themselves well to thetreatment of extravascular tissue, such as tumors, vascular electrodearrays may be formed and energized with RF energy to treat vascularailments, such as hemorrhages as well as vascular anomalies, e.g.,Arterio Vascular Malformation (AVM), Arterio Vascular Fistula (AVF),Venous Malformation (VM), and Lymphatic Malformation (LM). When RFenergy is applied to the vascular electrode array, the generation ofheat will shrink the collagen found in walls of small vessels (up to 3mm in diameter) until the lumen of each vessel is fully closed. Toensure that the vessels lumens close with little or no resistance, it isimportant that the embolic material be of a low viscosity and applied ata low pressure. Optionally, the electrically conductive solution is notembolic at all, so that it continues to flow through the vessels thathave not been fully closed, thereby allowing exposure the entire vesselnetwork to be exposed to RF energy until closure is achieved. In thiscase, it is important to relatively quickly apply the RF energy to theresulting vascular electrode array before it is absorbed into thesurrounding tissue. In this case, the balloon proximal to the electrodeof the catheter should be inflated prior to delivery of the embolicmaterial to help relieve pressure buildup due to blood flow, as well asto keep the embolic material from being diluted by blood. Because theelectrically conductive has a low viscosity, it can be distributedthrough the vessel network without the aid of the blood flow.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the scope of the present inventions as defined by theclaims.

1. A method of treating targeted tissue adjacent a physiologicalvascular network contoured to the general shape and size of the targetedtissue, comprising: delivering an electrically conductive materialwithin the vascular network, wherein the electrically conductivematerial embolizes in a region of the vascular network to form avascular electrode array that assumes a geometry of the embolized regionof the vascular network; and applying electrical energy to the vascularelectrode array to therapeutically conduct electrical energy into aregion of the targeted tissue adjacent the embolized region of thevascular network.
 2. The method of claim 1, wherein the embolized regionof the vascular network comprises the entirety of the vascular network,and the adjacent region of the targeted tissue comprises the entirety ofthe targeted tissue.
 3. The method of claim 1, wherein the vascularnetwork carries blood.
 4. The method of claim 1, wherein the vascularnetwork supplies blood to the targeted tissue.
 5. The method of claim 1,wherein the electrically conductive material is introduced into thevascular network and the electrical energy is applied to the vascularelectrode array via a single probe.
 6. The method of claim 1, whereinthe electrical energy is radio frequency (RF) energy.
 7. The method ofclaim 1, wherein the adjacent region of the targeted tissue is ablatedin response to the conduction of the electrical energy.
 8. The method ofclaim 1, wherein the vascular network comprises vessels that reduce insize at a periphery of the targeted tissue, and wherein the electricallyconductive material comprises particles, each of which is sized to lodgewithin a vessel at the periphery of the targeted tissue.
 9. The methodof claim 1, wherein the electrically conductive material comprisesembolic particles suspended within an electrically conductive solution.10. The method of claim 1, wherein the electrically conductive materialcomprises embolic particles doped with metallic sub-particles.
 11. Themethod of claim 1, wherein the embolic material has a viscosity that,when introduced into the vascular network, allows the embolic materialto naturally flow through the vascular network.
 12. The method of claim1, wherein the embolic material has a viscosity that, when theelectrical energy is applied, prevents the vascular network fromclosing.
 13. The method of claim 1, wherein the vascular electrode arraycomprises a main shaft and an array of tines extending from the mainshaft.
 14. The method of claim 1, wherein the embolic material isbiologically non-resorbable, so that the vascular electrode array ispermanent or semi-permanent, the method further comprising applyingadditional electrical energy to the vascular electrode array, wherebythe additional electrical energy is therapeutically conducted into anyanomalies in the corresponding region of targeted tissue region thathave occurred after the previous application of electrical energy. 15.The method of claim 1, further comprising delivering a containment agentwithin the vascular network proximal to the delivered electricallyconductive material to stabilize the vascular electrode array.
 16. Themethod of claim 1, wherein the targeted tissue is a tumor.
 17. A methodof treating a patient, comprising: delivering an electrically conductivematerial within a vascular network, wherein the electrically conductivematerial embolizes in the vascular network to form a vascular electrodearray that assumes a geometry of the vascular network; and applyingelectrical energy to the vascular electrode array to therapeuticallyconduct electrical energy into the vascular network. 18.-33. (canceled)34. A method of treating a patient, comprising: delivering anelectrically conductive material within a vascular network, wherein theelectrically conductive material has a viscosity that, when introducedinto the vascular network, allows the electrically conductive materialto naturally flow through the vascular network; delivering a containmentagent within the vascular network proximal to the delivered electricallyconductive material to stabilize the electrically conductive material,thereby forming a vascular electrode array that assumes a geometry ofthe vascular network; and applying electrical energy to the vascularelectrode array to therapeutically conduct electrical energy into thevascular network. 35.-46. (canceled)